Obtaining channel state information (CSI) through channel measurement is very important for improving transmission quality of wireless communication. During channel measurement, a receive end device (for example, user equipment such as a smartphone) obtains channel state information based on a reference signal (RS) transmitted by a transmit end device (for example, an access device such as a base station), and feeds back the obtained CSI to the transmit end device. The transmit end device processes a transmit signal based on the CSI and sends the processed transmit signal to the receive end device. It can be learned from the above that wireless transmission based on CSI is more compatible with a channel environment. Therefore, transmission quality is better.
The CSI may be usually sent from the receive end device to the transmit end device by using a physical uplink shared channel (PUSCH). The CSI transmitted by using the PUSCH may include wideband CSI, or may include a plurality of pieces of subband CSI, or may include both wideband CSI and a plurality of pieces of subband CSI. The wideband CSI may be understood as CSI obtained through calculation based on a wideband, and the subband CSI may be understood as CSI obtained through calculation based on a subband.
Usually, a network device needs to indicate a subband included in a CSI reporting band to a terminal, and the terminal performs CSI reporting on the indicated CSI reporting band. Sizes and quantity of subbands in the CSI reporting band need to be configured.
In the prior art, the quantity of subbands included in a CSI reporting band is configured based on a system bandwidth. However, with network evolution, this manner cannot be used for configuring the quantity of subbands included in a CSI reporting band.